The trick is to turn the key to the start position repeatedly about 10 times If they come on brightly, your battery is good and the clicking means you have either a bad connection or a bad starter. A fuel pressure gauge with the right fitting for your Cat Diesel, through the Amazon Affiliate Link: The pick-up says "CAT" on it.
#XPS PEAK FITTING CODE#
¹ The CID is a diagnostic code that indicates which component is faulty.